Former BHS owner Sir Philip Green has defended his management of the company, claiming he invested over £400m (€482m, $531m) in the business during his 15-year ownership.

In a letter addressed to MPs currently investigating the collapse of the 88-year old retail chain, Green said: "It is clear that we invested substantially in the business," adding he committed £421m to the business during his tenure.

BHS entered administration in April before eventually folding in June, after owing more than £1.1bn to various creditors, including a £571m pension deficit, £358m to landlords and £48.5m to suppliers.

Green, who sold the business to Dominic Chappell for £1 in 2015, has been heavily criticised by Westminster for his role in the demise of BHS.

"It is clear that we invested substantially in the business, we lent substantial sums to the business and we gave Retail Acquisitions [Chappell's consortium] every chance with a solid platform to take the business forward," he said in the letter.

The Arcadia Group tycoon, the fashion retailer that owns the likes of Top Shop and Dorothy Perkins, has been under intense pressure particularly for the £423m paid in dividends to his family and other BHS shareholders between 2000 and 2004.

Speaking before MPs last month, the former BHS owner insisted he will try to find a solution for the 20,000 people that have been affected by collapse. "We want to find a solution for the 20,000 pensioners," Green said, although he argued that putting the scheme into the Pension Protection Fund – the lifeboat for failed schemes would not resolve the issue, as the schemes are quite complex.

"I believe it is resolvable, it is solvable," he added. "We will sort it, we will find a solution."

Green's decision to sell the embattled retailer to Chappell, a man with no proven business background who had been declared bankrupt three times has also come under scrutiny.

Before he sold the company to Chappell, Green had turned down a bid put forward by a consortium led by Paul Sutton, a convicted fraudster. Crucially, however, Chappell told MPs he worked alongside Sutton when the latter was putting together the bid, something Green disputed when he appeared at Westminster.

In his letter, however, the fashion retail tycoon reiterated that he was unaware of Chappell's involvement with Sutton's bid. Meanwhile, Linklaters, the legal firm that acted as Green's legal advisers, said Chappell broke the terms of the sale agreement after failing to invest in BHS.

MPs are scheduled to publish their report on BHS collapse in the next two weeks.